BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Modeling a non-linear EPSPs integration site in dendrites and its 
 impact on computational capacities - Romain Cazé\, Group for Neural Theor
 y\, Ecole Normal Superieure\, Paris
DTSTART:20111124T160000Z
DTEND:20111124T170000Z
UID:TALK34777@talks.cam.ac.uk
CONTACT:Dr. Cristina Savin
DESCRIPTION:Integration of excitatory post synaptic potentials (EPSPs) in 
 dendrites can be locally non-linear. In a dendritic branch\, synchronous E
 PSPs can cause a local voltage response which overshoots their arithmetic 
 sum\, the so-called dendritic spike. This leads to the theoretical proposa
 l that a neuron can be seen as a network of non-linear subunits\, a model 
 with a higher computational capacity than classic models. However\, in pra
 ctice dendritic morphology can severely reduce the number of possible subu
 nits. This can be an issue\, because the number of independent subunits di
 rectly determines the increase in computational capacities. Thus\, in this
  study\, we take the most conservative hypothesis: we suppose the existenc
 e of a single non-linear dendritic subunit on top of linear somatic integr
 ation.\nTo model this hypothesis we use a binary neuron model\, the thresh
 old linear unit also known as the Perceptron\, and we add to it a non-line
 ar subunit. This subunit locally sums its synaptic inputs\, and passes it 
 though an all-or-none transfer function\, modeling a dendritic spike. We u
 se systematic parameter searches on this model to answer two questions: Ar
 e they computations - Boolean functions – enabled by a non-linear subuni
 t ? How well a computation which is possible with a non-linear subunit can
  be approximated without ?\nWe made two observations: first\, a non-linear
  subunit coupled with linear integration enables original computations\, f
 or instance the feature binding problem\; second\, this computation is the
  hardest to approximate without a non-linear subunit. We use these observa
 tions to implement the binding problem in a proof of principle biophysical
  model made of a soma and a single dendritic compartment. This demonstrate
 s that a very simple dendritic morphology\, a single branch\, already enha
 nces the computational capacities of single neuron.\n
LOCATION:Cambridge University Engineering Department\, CBL Rm #438 (http:/
 /learning.eng.cam.ac.uk/Public/Directions)
END:VEVENT
END:VCALENDAR